McCaffrey was given his marching orders by Barry Kelly at Parnell Park for an apparent late strike with the hurl on Galway’s Niall Cahalan as the pair contested a ball.
The 63rd minute sanction was met with some surprise as Cahalan was quickly back up on his feet and made no issue of the clash.
McCaffrey now faces at least a one-month ban which rules him out of Dublin’s league opener with Waterford on February 13 and, crucially, the Croke Park showdown with Tipperary six days later.
He will also miss Sunday’s Walsh Cup final, an honour which Dublin secured with a winning point in the 74th minute from Shane Ryan.
“How many times do we see that, a fella just mistiming it,” Dublin manager Anthony Daly said of McCaffrey’s pull.
“Johnny’s not a dirty player, his track record would be awful clean. That wouldn’t be his form at all.”
Asked if he would appeal the card, Daly said: “I don’t know. If we can we will.”
It was a good night for Dublin otherwise with Daly’s new recruits, in particular, impressing. Ryan, a former football All Star, shot three points including an impressive winner, while Conal Keaney’s 0-8 haul included a 70th-minute sideline conversion that levelled the scores.
Most impressive was former Tipperary senior Ryan O’Dwyer who engineered a wonderful solo goal in the 65th minute — just when Dublin needed it.
They were the better side throughout, though Galway goals from Eanna Ryan and Iarla Tannian left the Tribesmen one ahead with a minute of normal time remaining late intervention from Keaney and Ryan.
Scorers for Dublin: C Keaney 0-8 (7f, 1 s/l); R O’Dwyer 1-3; P Carton & S Ryan 0-3 each; J McCaffrey 0-2 (1 65); C McCormack 0-1.
Scorers for Galway: I Tannian 2-0; E Ryan 1-2; G Farragher 0-5 (2f); T Og Regan 0-3 (3f); D Burke, N Cahalan & J Coen 0-1 each.
DUBLIN: G Maguire; S Lambert, S Hiney, R Treanor; N Corcoran, J Boland, S Durkin; J McCaffrey, M O’Brien; C McCormack, R O’Dwyer, S Ryan; D O’Callaghan, C Keaney, P Carton.
Subs: D O’Dwyer for R O’Dwyer (22-26 blood), D Plunkett for O’Callaghan (54), D O’Dwyer for McCormack (59), R Walsh for Carton (62), L Ryan for R O’Dwyer (74).
GALWAY: J Grealish; D Collins, J Lee, D Hayes; D Barry, T Óg Regan, A Cullinane; N Cahalan, J Coen; G Farragher, K Kilkenny, A Smith; I Tannian, E Ryan, N Healy.
Subs: D Burke for Kilkenny (45), A Callanan for Cahalan (58).
Referee: B Kelly (Westmeath).